Unit 5 Study Guide: Microbial Diversity, Evolution of Vertebrates, and Animal Structure & Function

Microbial Diversity

Bacterial Shapes and Cell Wall Types

Bacteria are classified by their shapes and the structure of their cell walls, which are important for identification and understanding their biology.

• Bacilli: Rod-shaped bacteria.

• Cocci: Spherical bacteria.

• Spirochetes: Spiral-shaped bacteria, often motile.

• Gram-positive: Bacteria with thick peptidoglycan cell walls that retain the crystal violet stain in Gram staining.

• Gram-negative: Bacteria with thin peptidoglycan layers and an outer membrane; do not retain the crystal violet stain.

• Peptidoglycan: A polymer that forms a mesh-like layer outside the plasma membrane of most bacteria, providing structural strength.

Example: Staphylococcus aureus is a Gram-positive coccus; Escherichia coli is a Gram-negative bacillus.

Metabolic Types in Prokaryotes

Prokaryotes are classified by how they obtain energy and carbon.

• Chemoautotrophs: Obtain energy from inorganic chemicals and carbon from CO2.

• Chemoheterotrophs: Obtain both energy and carbon from organic molecules.

• Photoautotrophs: Use light as an energy source and CO2 as a carbon source (e.g., cyanobacteria).

• Photoheterotrophs: Use light for energy but obtain carbon from organic compounds.

Archaea and Extremophiles

Archaea are prokaryotes distinct from bacteria, often found in extreme environments.

• Methanogens: Produce methane as a metabolic byproduct; often found in anaerobic environments.

• Thermophiles: Thrive in very hot environments, such as hot springs.

Protists: Diversity and Structure

Protists are a diverse group of mostly unicellular eukaryotes.

• Diatoms: Unicellular algae with silica cell walls; important primary producers in aquatic environments.

• Dinoflagellates: Mostly marine plankton; some cause harmful algal blooms (red tides).

• Brown algae: Large, multicellular algae (e.g., kelp); important in marine ecosystems.

• Pseudopodia: Extensions of the cell used for movement and feeding in some protists (e.g., amoebas).

• Foraminiferans: Protists with porous shells (tests) made of calcium carbonate; use pseudopodia.

• Radiolarians: Protists with intricate silica skeletons; also use pseudopodia.

• Flagella: Whip-like structures used for movement in many protists and some bacteria.

Evolution of Vertebrates and Mammals

Major Groups and Characteristics

Vertebrates are animals with backbones, and their evolution includes several key groups and adaptations.

• Monotremes: Egg-laying mammals (e.g., platypus, echidna).

• Marsupials: Mammals with pouches; young are born early and complete development in the pouch (e.g., kangaroo).

• Mammals: Vertebrates with hair and mammary glands; include monotremes, marsupials, and placental mammals.

• Tetrapods: Vertebrates with four limbs (amphibians, reptiles, birds, mammals).

• Amniotes: Vertebrates with an amniotic egg, allowing reproduction on land (reptiles, birds, mammals).

• Ectothermic: Animals that rely on external sources for body heat (e.g., reptiles, amphibians).

• Endothermic: Animals that regulate their own body temperature internally (e.g., birds, mammals).

Scientific view of birds: Birds are considered a group of reptiles, specifically descended from theropod dinosaurs.

Evolutionary Trees

Evolutionary trees (phylogenies) show relationships among groups. Branch points represent common ancestors, and the order of branching indicates evolutionary relationships.

• To interpret a tree, follow the branches from the root to the tips, noting where groups diverge.

• Major characteristics (e.g., amniotic egg, hair) are often mapped onto the tree to show when they evolved.

Animal Structure and Function

Levels of Organization

Multicellular organisms are organized hierarchically:

• Molecule → Cell → Tissue → Organ → Organ system → Organism

Organ: A structure composed of two or more tissue types that performs a specific function.

Organ system: A group of organs that work together to perform major body functions.

Tissue: A group of similar cells that perform a specific function.

Organism: An individual living thing.

Tissues: Types and Functions

There are four major categories of animal tissues:

• Epithelial tissue: Covers body surfaces and lines cavities; functions in protection, absorption, and secretion.

• Connective tissue: Supports, binds, and protects other tissues and organs.

• Muscle tissue: Responsible for movement.

• Nervous tissue: Transmits electrical signals; coordinates body activities.

Examples of Tissues

• Epithelial: Skin epidermis, lining of the gut.

• Connective: Bone, blood, cartilage, adipose (fat).

• Muscle: Skeletal muscle, cardiac muscle, smooth muscle.

• Nervous: Brain, spinal cord, nerves.

Types of Epithelial Tissues

Epithelial tissues are named based on the number of layers and the shape of the cells:

• Simple: One cell layer thick.

• Stratified: Multiple layers.

• Squamous: Flat cells.

• Cuboidal: Cube-shaped cells.

• Columnar: Tall, column-like cells.

Naming convention: Combine the number of layers and cell shape (e.g., simple squamous epithelium).

Types of Connective Tissues and Their Characteristics

Type	Defining Characteristics	Location/Function
Loose connective tissue	Loose weave of fibers	Under skin; binds epithelia to underlying tissues
Fibrous connective tissue	Dense with collagen fibers	Tendons, ligaments
Adipose tissue	Stores fat in large cells	Energy storage, insulation
Cartilage	Flexible, rubbery matrix	Joints, ear, nose
Bone	Rigid matrix of collagen and calcium salts	Skeletal support
Blood	Cells in a liquid matrix (plasma)	Transport of gases, nutrients, wastes

Most common type: Loose connective tissue is the most widespread connective tissue in the human body.

Types of Muscle Tissues and Their Functions

Type	Function	Location
Skeletal muscle	Voluntary movement	Attached to bones
Cardiac muscle	Pumps blood	Heart
Smooth muscle	Involuntary movement	Walls of digestive tract, blood vessels

Nervous Tissue

• Neurons: Nerve cells that transmit electrical impulses.

• Nerve: A bundle of neuron fibers (axons) in the peripheral nervous system.

Plasma

Plasma: The liquid component of blood, in which blood cells are suspended; contains water, proteins, nutrients, hormones, and waste products.

Organs of the Respiratory System

• Nasal cavity

• Pharynx

• Larynx

• Trachea

• Bronchi

• Lungs

• Alveoli (site of gas exchange)

Homeostasis and Feedback Mechanisms

Homeostasis

Homeostasis: The maintenance of a stable internal environment despite changes in external conditions.

Feedback Mechanisms

• Negative feedback: A control mechanism that reduces or reverses a change to maintain homeostasis. Example: Regulation of body temperature; if body temperature rises, mechanisms are activated to cool the body.

• Positive feedback: A control mechanism that amplifies a change. Example: Blood clotting; during childbirth, contractions increase in intensity due to positive feedback.

Physiologist

Physiologist: A scientist who studies the functions and mechanisms of living organisms and their parts.

Structure and Function

In biology, the structure of a biological component is closely related to its function. For example, the thin, flat shape of alveoli in the lungs increases surface area for gas exchange.

Summary Table: Tissue Types and Functions

Tissue Type	Function	Location
Epithelial	Protection, absorption, secretion	Skin, lining of organs
Connective	Support, binding, transport	Bone, blood, fat
Muscle	Movement	Skeletal muscles, heart, digestive tract
Nervous	Signal transmission	Brain, nerves, spinal cord

Additional info: Some details, such as the naming of epithelial tissues and the most common connective tissue, were expanded for clarity and completeness.